class_docstr: Holds utility methods to work with a tokenized text and entity spans.
  
  Spans must be tuples containing the label (str), start char idx (int), and end char idx (int).
  
  Args:
      text: The text the spans refer to.
      tokens: The tokens of the text.
docstr: The char index to token index mapping.
docstr_tok: ["The","char","index","to","token","index","mapping","."]
code: def char_to_token_idx(self) -> Dict[int, int]:
      """The char index to token index mapping."""
      return self._char_to_token_idx
  
file_path: argilla/src/argilla/utils/span_utils.py
imports: from typing import Dict, List, Optional, Tuple
label_desc: Use image node_id 5 for calling the SpanUtils obj's underlying member method code with example usage: obj.char_to_token_idx() and returns: self